transatlantic slave trade, segment of the global slave trade that transported between 10 million and 12 million enslaved Africans across the Atlantic Ocean to the Americas from the 16th to the 19th century. It was the second of three stages of the so-called triangular trade, in which arms, textiles, and wine were shipped from Europe to Africa, enslaved people from Africa to the Americas, and sugar and coffee from the Americas to Europe.

Origins of the transatlantic trade of enslaved people

By the 1480s Portuguese ships were already transporting Africans for use as enslaved labourers on the sugar plantations in the Cape Verde and Madeira islands in the eastern Atlantic. Spanish conquistadors took enslaved Africans to the Caribbean after 1502, but Portuguese merchants continued to dominate the transatlantic slave trade for another century and a half, operating from their bases in the Congo-Angola area along the west coast of Africa. The Dutch became the foremost traders of enslaved people during parts of the 1600s, and in the following century English and French merchants controlled about half of the transatlantic slave trade, taking a large percentage of their human cargo from the region of West Africa between the Sénégal and Niger rivers. In 1713 an agreement between Spain and Britain granted the British a monopoly on the trade of enslaved people with the Spanish colonies. Under the Asiento de negros, Britain was entitled to supply those colonies with 4,800 enslaved Africans per year for 30 years. The contract for this supply was assigned to the South Sea Company, of which British Queen Anne held some 22.5 percent of the stock.

Probably no more than a few hundred thousand Africans were taken to the Americas before 1600. In the 17th century, however, demand for enslaved labour rose sharply with the growth of sugar plantations in the Caribbean and tobacco plantations in the Chesapeake region in North America. The largest numbers of enslaved people were taken to the Americas during the 18th century, when, according to historians’ estimates, nearly three-fifths of the total volume of the transatlantic slave trade took place.

The slave trade had devastating effects in Africa. Economic incentives for warlords and tribes to engage in the trade of enslaved people promoted an atmosphere of lawlessness and violence. Depopulation and a continuing fear of captivity made economic and agricultural development almost impossible throughout much of western Africa. A large percentage of the people taken captive were women in their childbearing years and young men who normally would have been starting families. The European enslavers usually left behind persons who were elderly, disabled, or otherwise dependent—groups who were least able to contribute to the economic health of their societies.

Historians have debated the nature and extent of European and African agency in the actual capture of those who were enslaved. During the early years of the transatlantic slave trade, the Portuguese generally purchased Africans who had been enslaved during tribal wars. As the demand for enslaved people grew, the Portuguese began to enter the interior of Africa to forcibly take captives; as other Europeans became involved in the slave trade, generally they remained on the coast and purchased captives from Africans who had transported them from the interior. Following capture, the abducted Africans were marched to the coast, a journey that could be as many as 300 miles (485 km). Typically, two captives were chained together at the ankle, and columns of captives were tied together by ropes around their necks. An estimated 10 to 15 percent of the captives died on their way to the coast.